Refrigerating and air-conditioning apparatus

ABSTRACT

A refrigerating and air-conditioning apparatus performs, even during a heating operation under air conditions leading to formation of frost, a defrosting operation while simultaneously continuing the heating operation and improves comfort through heating by securing an appropriate amount of ventilation. A plurality of refrigeration cycles independently performs a heating operation and a defrosting operation. By controlling a ventilation damper of an indoor unit that is to perform a defrosting operation to increase the amount of ventilation, a prior ventilation operation for securing the time-averaged required amount of ventilation including the period in which the defrosting operation is being performed is performed before the defrosting operation, and after the prior ventilation is terminated, the defrosting operation is started.

TECHNICAL FIELD

The present invention relates to a refrigerating and air-conditioningapparatus by a vapor-compression refrigeration cycle, and in particular,to a refrigerating and air-conditioning apparatus that is capable of,even during a heating operation under air conditions leading toformation of frost, performing a defrosting operation whilesimultaneously continuing the heating operation.

BACKGROUND ART

As a refrigerating and air-conditioning apparatus which includes aplurality of refrigeration cycles and which is capable of performing adefrosting operation while simultaneously continuing a heatingoperation, for example, there has been an air-conditioning apparatus forvehicle described in Patent Literature 1. With the arrangement in whicha refrigeration cycle which performs defrosting by a cooling operationand a refrigeration cycle which continues a heating operation areindividually provided within the vehicle, the air-conditioning apparatusfor vehicle is able to perform a defrosting operation whilesimultaneously continuing a heating operation.

Furthermore, as an air-conditioning apparatus for vehicle described inPatent Literature 2, a technique to maintain comfort by adjusting theamount of ventilation according to a vehicle occupancy, is disclosed.

CITATION LIST Patent Literature

Patent Literature 1: Japanese Unexamined Patent Application PublicationNo. 2006-116981 (claim 1, FIG. 1)

Patent Literature 2: Japanese Patent No. 4346429 (claim 1)

SUMMARY OF INVENTION Technical Problem

In Patent Literature 1, an indoor heat exchanger of the refrigerationcycle that performs a heating operation is caused to act as a condenser,while an indoor heat exchanger of the refrigeration cycle that performsa defrosting operation is caused to act as an evaporator. Then, airpassing through each of the indoor heat exchangers is sucked by a sharedindoor fan, is mixed within the casing of the indoor fan, and is blownout into the room as conditioned air. Therefore, there is a problem thatthe outlet air temperature may be lowered, causing discomfort topassengers. Because the air is sent to an outdoor heat exchanger(evaporator) by operating an outdoor fan during the defrostingoperation, the condensing temperature may not rise when the outside airtemperature is low, thereby causing a possibility that defrosting is notperformed.

Furthermore, during the defrosting operation while performing theheating operation, it is preferred that the room is ventilated with anappropriate amount of ventilation. In Patent Literature 2, althoughventilation during a cooling operation is considered, ventilation duringa defrosting operation is not particularly considered.

The present invention has been made in view of the above problems.Therefore, it is an object of the present invention to provide arefrigerating and air-conditioning apparatus which is capable of, evenduring a heating operation under air conditions leading to formation offrost, performing a defrosting operation while simultaneously continuinga heating operation and which improves comfort through heating bysecuring an appropriate amount of ventilation.

Solution to Problem

A refrigerating and air-conditioning apparatus according to the presentinvention includes a plurality of refrigeration cycles that each includea compressor, a four-way valve, an outdoor heat exchanger, a pressurereducing device, and an indoor heat exchanger that are connected to oneanother, the plurality of refrigeration cycles being capable ofindependently performing a heating operation and a defrosting operation;an outdoor unit that includes the compressor, the four-way valve, andthe outdoor heat exchanger; a plurality of indoor units that eachinclude the ventilation port, a ventilation damper for opening andclosing the ventilation port, an indoor fan for taking in outside airthrough the ventilation port and sending the air into a room, and theindoor heat exchanger, the plurality of indoor units being installablein a same room; and a controller that controls the ventilation damper toperform indoor ventilation during the heating operation, and thatcontrols the ventilation damper of each of the plurality of indoor unitsto close the corresponding ventilation port and stop indoor ventilationduring a defrosting operation. Prior to a defrosting operation, thecontroller performs a prior ventilation operation for securing atime-averaged required amount of ventilation including a period in whichthe defrosting operation is being performed by controlling theventilation damper of the indoor unit of a refrigeration cycle that isto perform the defrosting operation to increase the amount ofventilation, and after termination of the prior ventilation operation,the controller starts the defrosting operation.

Advantageous Effects of Invention

According to the present invention, it is possible to perform adefrosting operation while simultaneously continuing a heating operationby providing a plurality of refrigeration cycles that are capable ofperforming the heating operation and the defrosting operationindependently. In addition, since a ventilation damper is closed after aprior ventilation operation is performed before a defrosting operationto secure a sufficient amount of ventilation, a continuous heatingoperation is performed while securing the time-averaged required amountof ventilation, thus achieving the improvement of comfort.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a refrigerant circuit diagram of a refrigerating andair-conditioning apparatus according to Embodiment 1 of the presentinvention.

FIG. 2 is a schematic cross-sectional view of an outdoor unit in FIG. 1.

FIG. 3 is a control block diagram of the refrigerating andair-conditioning apparatus in FIG. 1.

FIG. 4 is a timing chart of an operation example 1 of the refrigeratingand air-conditioning apparatus according to Embodiment 1 of the presentinvention.

FIG. 5 is a timing chart of an operation example 2 of the refrigeratingand air-conditioning apparatus according to Embodiment 1 of the presentinvention.

FIG. 6 is a timing chart of an operation example 3 of the refrigeratingand air-conditioning apparatus according to Embodiment 1 of the presentinvention.

FIG. 7 is a timing chart of an operation example 4 of the refrigeratingand air-conditioning apparatus according to Embodiment 1 of the presentinvention.

FIG. 8 is a refrigerant circuit diagram of a refrigerating andair-conditioning apparatus according to Embodiment 2 of the presentinvention.

DESCRIPTION OF EMBODIMENTS

Hereinafter, preferred embodiments of a refrigerating andair-conditioning apparatus according to the present invention will bedescribed, with reference to the accompanying drawings.

Embodiment 1

(Refrigerant Circuit Configuration)

FIG. 1 is a refrigerant circuit diagram of a refrigerating andair-conditioning apparatus according to Embodiment 1 of the presentinvention. FIG. 2 is a schematic cross-sectional view of an outdoor unitin FIG. 1. In FIGS. 1 and 2 and the figures described below, objectswith the same reference numerals are referred to as being equal to orcorresponding to one another, which is common throughout the full textof the description.

The refrigerating and air-conditioning apparatus according to Embodiment1 is, for example, used as an air-conditioning apparatus for vehicle,and includes an outdoor unit 1, and indoor units 2 a and 2 b which areinstallable in the same room. A first refrigeration cycle is configuredby connecting the outdoor unit 1 and the indoor unit 2 a, and a secondrefrigeration cycle is configured by connecting the outdoor unit 1 andthe indoor unit 2 b.

The first refrigeration cycle includes a compressor 3 a, a four-wayvalve 4 a, an outdoor heat exchanger 5 a, a pressure reducing device 6a, and an indoor heat exchanger 7 a, which are sequentially connected bypipes, and is configured so that a refrigerant is able to circulatethrough the first refrigeration cycle. The first refrigeration cycle isconfigured to be capable of switching the operation mode between acooling operation (defrosting operation) and a heating operation by thefour-way valve 4 a switching the flow path of the refrigerant dischargedfrom the compressor 3 a. The indoor unit 2 a, in which part of the firstrefrigeration cycle is arranged, includes an indoor heat exchanger 7 a,an indoor fan 8 a, a ventilation port 9 a to take in the outside air, aventilation damper 10 a which has an opening and closing function foropening and closing the ventilation port 9 a, and an air inlet 11 a forindoor air.

The second refrigeration cycle includes a compressor 3 b, a four-wayvalve 4 b, an outdoor heat exchanger 5 b, a pressure reducing device 6b, and an indoor heat exchanger 7 b, which are sequentially connected bypipes, and is configured so that a refrigerant is able to circulatethrough the second refrigeration cycle. The first refrigeration cycle isconfigured to be capable of switching the operation mode between acooling operation (defrosting operation) and a heating operation by thefour-way valve 4 b switching the flow path of the refrigerant dischargedfrom the compressor 3 b. The indoor unit 2 b, in which part of thesecond refrigeration cycle is arranged, includes an indoor heatexchanger 7 b, an indoor fan 8 b, a ventilation port 9 b to take in theoutside air, a ventilation damper 10 b which has an opening and closingfunction, and an air inlet 11 b for indoor air.

In addition, the outdoor unit 1 includes an outdoor fan 12 for sendingthe outside air into the outdoor heat exchanger 5 a and the outdoor heatexchanger 5 b.

Furthermore, the refrigerating and air-conditioning apparatus includes acontroller 13 for controlling the switching of the operation modes bythe four-way valves 4 a and 4 b, the opening and closing of theventilation dampers 10 a and 10 b, and the operation of the indoor fans8 a and 8 b and the compressors 3 a and 3 b. FIG. 1 illustrates theconfiguration of the refrigerating and air-conditioning apparatus whichincludes two refrigeration cycles. However, the refrigerating andair-conditioning apparatus may be configured to include a furtherplurality of refrigeration cycles. Moreover, the number of the indoorunits installable is not limited to two, and a further plurality ofindoor units may be installable.

(Sensor Configuration)

The indoor unit 2 a includes, at an air inlet for the indoor air orinside the room, an indoor temperature sensor 14 a for detecting theindoor temperature and an indoor humidity sensor 15 a for detecting theindoor humidity. Similarly, the indoor unit 2 b side also includes anindoor temperature sensor 14 b for detecting the indoor temperature andan indoor humidity sensor 15 b for detecting the indoor humidity.

The outdoor unit 1 includes, at the air inlet of the outdoor fan 12 oroutside the apparatus, outside air temperature sensors 16 a and 16 b(see FIG. 2), for detecting the outside air temperature. Furthermore,the outdoor unit 1 includes a temperature sensor 17 a for detecting thetemperature of a pipe positioned between the outdoor heat exchanger 5 aand the pressure reducing device 6 a, and a temperature sensor 17 b fordetecting the temperature of a pipe positioned between the outdoor heatexchanger 5 b and the pressure reducing device 6 b.

FIG. 3 is a control block diagram of the refrigerating andair-conditioning apparatus in FIG. 1.

The controller 13 includes a CPU, a RAM for storing various data, and aROM for storing a program for operating the refrigerating andair-conditioning apparatus (none of the CPU, the RAM, and the ROM areillustrated). With this configuration, a room occupancy detection unit13 a, an air-conditioning capacity setting unit 13 b, anamount-of-ventilation setting unit 13 c, a defrosting startdetermination unit 13 d, and a defrosting end determination unit 13 eare functionally configured in the controller 13.

The room occupancy detection unit 13 a detects the number of occupantsin the room, based on information detected by a weight sensor (notillustrated), an image pickup device (not illustrated), or the like,provided in the room.

The air-conditioning capacity setting unit 13 b detects theair-conditioning load based on the outside air temperature detected bythe outside air temperature sensors 16 a and 16 b, the indoortemperature detected by the indoor temperature sensors 14 a and 14 b,and a preset indoor temperature. Based on the detected air-conditioningload, the air-conditioning capacity setting unit 13 b sets a requiredair-conditioning capacity. The air-conditioning capacity setting unit 13b may also correct the required air-conditioning capacity on the basisof the number of occupants in the room detected by the room occupancydetection unit 13 a.

The amount-of-ventilation setting unit 13 c detects ventilation loadbased on an output signal of an oxygen concentration sensor (notillustrated) or a carbon dioxide sensor (not illustrated), provided inthe room, and sets a required amount of ventilation based on thedetected ventilation load. The amount-of-ventilation setting unit 13 cmay estimate the required amount of ventilation based on the number ofoccupants in the room detected by the room occupancy detection unit 13a. Setting of the amount of ventilation by the amount-of-ventilationsetting unit 13 c is performed repeatedly during the heating operation,and the required amount of ventilation is updated according to thecurrent ventilation state, the number of occupants in the room, and thelike.

Details of the defrosting start determination unit 13 d and thedefrosting end determination unit 13 e will be described later.

The compressor 3 a, the four-way valve 4 a, the indoor fan 8 a, theventilation damper 10 a, the indoor temperature sensor 14 a, the indoorhumidity sensor 15 a, and the temperature sensor 17 a of the firstrefrigeration cycle side are connected to the controller 13.Furthermore, the compressor 3 b, the four-way valve 4 b, the indoor fan8 b, the ventilation damper 10 b, the indoor temperature sensor 14 b,the indoor humidity sensor 15 b, and the temperature sensor 17 b of thesecond refrigeration cycle side are also connected to the controller 13.Moreover, an input unit 18 for setting the indoor temperature andinputting and changing set values of various controls is also connectedto the controller 13.

(Ventilation Operation)

Next, the operation of a ventilation operation in the refrigerating andair-conditioning apparatus of Embodiment 1 will be explained. Theventilation operation is able to be performed independently on indoorunits 2 a and 2 b. The operations of the indoor units 2 a and 2 b areboth the same. Therefore, a ventilation operation will be explainedhereinafter, with the operation of the indoor unit 2 a.

The ventilation operation is an operation for taking in the outside airthrough the ventilation port 9 a by operating the indoor fan 8 a andopening the ventilation damper 10 a so that the air is supplied into theroom. The ventilation damper 10 a repeatedly alternates between theopening and dosing operations, and the amount of ventilation iscontrolled by the control of the opening and closing rate (the ratio ofan opening time to one cycle of opening and closing) of the opening andclosing operations by the ventilation damper 10 a. In the ventilationoperation, the opening and closing rate is determined so that the amountof ventilation (the required amount of ventilation) set by theamount-of-ventilation setting unit 13 c is secured on a time averagebasis, and by performing the opening and closing operations for theventilation damper 10 a according to the opening and closing rate, therequired amount of ventilation is secured on a time average basis. Theamount-of-ventilation setting unit 13 c may store in advance the amountof ventilation per predetermined time (for example, one second) whilethe ventilation damper 10 a is open, and may determine the opening andclosing rate based on the amount of ventilation, the duration of onecycle of opening and closing (for example, one minute), and the requiredamount of ventilation.

However, the control of the amount of ventilation is not limited to theabove method and may also be performed in accordance with the openingratio of the ventilation port 9 a. The ventilation operation iscontrolled independently of a cooling operation and a heating operation,which will be described below. Accordingly, each of the firstrefrigeration cycle and the second refrigeration cycle may perform theventilation operation while a cooling operation is being performed, orperform the ventilation operation while a heating operation is beingperformed. It should be noted that a defrosting operation and theventilation operation are not performed at the same time.

(Cooling Operation)

Next, the operation of a refrigeration cycle for a cooling operation inthe refrigerating and air-conditioning apparatus of this embodiment willbe explained. A four-way valve is switched to the dotted line side inFIG. 1 in the cooling operation. The first refrigeration cycle and thesecond refrigeration cycle are able to perform a cooling operationindependently. The cooling operations of the first refrigeration cycleand the second refrigeration cycle are both the same. Therefore, acooling operation will be explained hereinafter, with the coolingoperation of the first refrigeration cycle.

In the cooling operation, the refrigerant compressed and heated in thecompressor 3 a flows into the outdoor heat exchanger 5 a via thefour-way valve 4 a. The refrigerant which has flowed into the outdoorheat exchanger 5 a is cooled and condensed by exchanging heat with theoutside air sent by the outdoor fan 12. Then, the pressure of therefrigerant is reduced by the pressure reducing device 6 a, and therefrigerant is heated and evaporated in the indoor heat exchanger 7 a byexchanging heat with the indoor air sent by the indoor fan 8 a, Therefrigerant then flows into the compressor 3 a, and completes one cycle.The room is cooled down by repeating the above-mentioned cyclecontinuously.

In the cooling operation, the air sucked into the indoor unit 2 a by theindoor fan 8 a is the mixed air of the outside air flowing in throughthe ventilation port 9 a and the indoor air flowing in through the airinlet 11 a, when the ventilation damper 10 a is open. The mixed aircools down by exchanging heat with the indoor heat exchanger 7 a, and isblown out into the room. When the ventilation damper 10 a is closed, theindoor air which flows in through the air inlet 11 a cools down byexchanging heat with the indoor heat exchanger 7 a, and is blown outinto the room.

(Heating Operation)

Next, the operation of a refrigeration cycle for a heating operation inthe refrigerating and air-conditioning apparatus of Embodiment 1 will beexplained. A four-way valve is switched to the solid line side in FIG. 1in the heating operation. The first refrigeration cycle and the secondrefrigeration cycle are able to perform a heating operationindependently. The heating operations of the first refrigeration cycleand the second refrigeration cycle are both the same. Therefore, aheating operation will be explained hereinafter, with the heatingoperation of the first refrigeration cycle.

In the heating operation, the refrigerant compressed and heated in thecompressor 3 a flows into the indoor heat exchanger 7 a via the four-wayvalve 4 a. The refrigerant which has flowed into the indoor heatexchanger 7 a is cooled and condensed by exchanging heat with the indoorair sent by the indoor fan 8 a. Then, the pressure of the refrigerant isreduced by the pressure reducing device 6 a, and the refrigerant isheated and evaporated in the outdoor heat exchanger 5 a by exchangingheat with the outside air sent by the outdoor fan 12. The refrigerantthen flows into the compressor 3 a, and completes one cycle. The room isheated by repeating the above-mentioned cycle continuously.

In the heating operation, the air sucked into the indoor unit 2 a by theindoor fan 8 a is the mixed air of the outside air flowing in throughthe ventilation port 9 a and the indoor air flowing in through the airinlet 11 a, when the ventilation damper 10 a is open. The mixed aircools down by exchanging heat with the indoor heat exchanger 7 a, and isblown out into the room. When the ventilation damper 10 a is closed, theindoor air which flows in through the air inlet 11 a is heated byexchanging heat with the indoor heat exchanger 7 a, and is blown outinto the room.

(Defrosting Operation)

Next, the operation of a defrosting operation in the refrigerating andair-conditioning apparatus of Embodiment 1 will be explained. The firstrefrigeration cycle and the second refrigeration cycle are able toperform a defrosting operation independently. The defrosting operationsof the first refrigeration cycle and the second refrigeration cycle areboth the same. Therefore, a defrosting operation will be explainedhereinafter, with the defrosting operation of the first refrigerationcycle.

During a heating operation, when the outside air temperature is low andthe evaporating temperature of the outdoor heat exchanger 5 a is at orbelow 0 degrees Celsius, moisture contained in the outside air is frozenon the outdoor heat exchanger 5 a, and frost is generated (formation offrost). When frost is formed on the outdoor heat exchanger 5 a, the airflow decreases due to clogging of the fins, and furthermore, since theheat transmission is impeded by the frost layer, the amount of heatgained from the outside air decreases and the heating capacity is thusreduced. Therefore, a defrosting operation to melt the frost on theoutdoor heat exchanger 5 a is performed on a regular basis.

The defrosting start determination unit 13 d determines whether or notdefrosting of the outdoor heat exchanger 5 a in the refrigeration cycleneeds to start in the heating operation. Regarding the determination asto whether or not defrosting needs to be performed, for example, it isdetermined that defrosting needs to start when the saturationtemperature, that is, the evaporating temperature, of the refrigerant inthe outdoor heat exchanger 5 a is at or below 0 degrees Celsius and thedifference between the outside air temperature and the evaporatingtemperature is equal to or greater than a predetermined temperaturedifference (for example, 15 degrees Celsius). Furthermore, if the amountof frost formation can be estimated in advance, the heating operationtime may be measured, and the determination as to start of defrostingmay be made using a timer. The determination by the defrosting startdetermination unit 13 d as to whether or not defrosting needs to startis not limited to the methods described above. In addition, for example,a reduction in the amount of cooing or the amount of frost formation ofthe outdoor heat exchanger 5 a may be detected and the determination maybe made based on the result of the detection.

The defrosting end determination unit 13 e determines whether adefrosting operation is to be terminated. Regarding the determination asto whether a defrosting operation is to be terminated, for example, whenthe temperature detected by the temperature sensor 17 a has reached apredetermined temperature (for example, 10 degrees Celsius), it isdetermined that frost on the outdoor heat exchanger 5 a has melted andthat defrosting is to be terminated. Furthermore, if the amount ofdefrosting can be estimated in advance, the defrosting operation timemay be measured and the determination as to termination of defrostingmay be made using a timer. The determination by the defrosting enddetermination unit 13 e as to termination of defrosting is not limitedto the methods described above. In addition, for example, recovery ofthe amount of cooling or the amount of frost formed on the outdoor heatexchanger 5 a may be detected, and the determination may be made basedon the result of the detection.

In performing a defrosting operation, there is no heating capacity inthe refrigeration cycle that performs the defrosting operation.Therefore, if one of the two refrigeration cycles enters a defrostingoperation, the other refrigeration cycle performs a heating operation,so that indoor heating continues to be performed. Furthermore, duringthe defrosting operation, in order to prevent a drop in the roomtemperature caused by introduction of outside air, the operation isperformed when the ventilation dampers 10 a and 10 b of the indoor units2 a and 2 b are closed. That is, a ventilation operation is stoppedduring a defrosting operation.

A defrosting operation includes off-cycle defrosting and reversedefrosting. The operations of the off-cycle defrosting and the reversedefrosting will be described below. Here, the first refrigeration cyclewill be explained by way of example.

(Off-cycle Defrosting)

The off-cycle defrosting is an operation for defrosting using heat ofthe outside air by stopping the compressor 3 a, operating the outdoorfan 12, and sending the outside air to the outdoor heat exchanger 5 awhen the outside air temperature is above a predetermined temperature.When the outside air is at or above 0 degrees Celsius, frost melts.Therefore, the predetermined temperature may be set to about 5 degreesCelsius to secure melting. The off-cycle defrosting is excellent inenergy saving since the compressor 3 a is stopped. Furthermore, sincethe indoor heat exchanger 7 a does not act as an evaporator unlikereverse defrosting, which will be described later, the room temperaturecan be prevented from dropping. That is, when the outside airtemperature is at or above 5 degrees Celsius, off-cycle defrosting iseffective in terms of energy saving.

(Reverse Defrosting)

When the outside air temperature is at 5 or below degrees Celsius,defrosting cannot be performed with off-cycle defrosting. Therefore, areverse defrosting operation using the heat of refrigerant is performed.When explanation of reverse defrosting will be given with the firstrefrigeration cycle as an example, the reverse defrosting is anoperation for defrosting using the condensing heat of refrigerant byswitching the four-way valve 4 a from a heating circuit to a coolingcircuit, so that the refrigerant that has been compressed by thecompressor 3 a into a high-temperature and high-pressure state is causedto flow into the outdoor heat exchanger 5 a.

In addition, although in the reverse defrosting a defrosting operationis generally performed by stopping the indoor fan 8 a and the outdoorfan 12 (fan operation control 1), the indoor fan 8 a and the outdoor fan12 may be operated. For example, the indoor fan 8 a may be operated whenthe heating load is smaller than or equal to a predetermined value andthe indoor fan 8 a may be stopped when the heating load is greater thanthe predetermined value (fan operation control 2). In the case where theindoor fan 8 a is operated in the reverse defrosting, defrosting of theoutdoor heat exchanger 5 a can be achieved using the heat of the indoorair. Therefore, the defrosting time can further be shortened. Since coldair is blown when the indoor fan 8 a operates, the indoor fan 8 a shouldbe operated only when the heating load is smaller than or equal to thepredetermined value.

Furthermore, the outdoor fan 12 may be operated when the outside airtemperature detected by the outside air temperature sensor 16 a is at orabove a predetermined value and the outdoor fan 12 may be stopped whenthe outside air temperature detected by the outside air temperaturesensor 16 a is below the predetermined value (fan operation control 3).In the case where the outdoor fan 12 is operated in the reversedefrosting, since a larger amount of heat can be acquired from theoutside air with the other heating operation cycle, the heating capacitycan be increased. Since the outside air at a low temperature impedesdefrosting when the outdoor fan 12 operates, the outdoor fan 12 shouldbe operated only when the outside air temperature is at or above thepredetermined value.

Furthermore, reverse defrosting can be performed even when the outsideair temperature is at or above 5 degrees Celsius. Since the compressor 3a is operated, the defrosting time can be shortened compared to offcycle defrosting. Furthermore, in the case where the indoor fan 8 a isoperated with the reverse defrosting, since defrosting of the outdoorheat exchanger 5 a can be achieved using the heat of the indoor air, thedefrosting time can further be shortened.

(Defrosting Operation Control Operation)

Next, a defrosting operation control operation with ventilation load andheating load will be explained. Although repetitive explanation will begiven, in the case where a defrosting operation is performed, sincethere is no heating capacity in the refrigeration cycle on thedefrosting operation side, one of two refrigeration cycles performsdefrosting and the other refrigeration cycle performs a heatingoperation. At this time, the operations are performed when theventilation dampers 10 a and 10 b in the indoor units 2 a and 2 b areclosed. With the operations described above, the refrigerating andair-conditioning apparatus is capable of reducing the heating load byblocking the introduction of the outside air during the defrostingoperation and is capable of performing the defrosting operation whilesecuring the heating capacity by defrosting alternately between thefirst refrigeration cycle and the second refrigeration cycle.

Here, the overview of a defrosting operation control operation during aheating operation will be explained. Since a ventilation operation isstopped during a defrosting operation, there is a possibility of ashortage of ventilation during the defrosting operation unless anymeasures are taken. Therefore, before starting a defrosting operation, aprior ventilation operation for securing the time-averaged requiredamount of ventilation including the period during which the defrostingoperation is being performed is performed. After that, the defrostingoperation is entered. In the prior ventilation operation, an operationfor controlling the opening and closing operation ratio of theventilation dampers 10 a and 10 b to increase the amount of ventilationto be greater than the amount of ventilation in a normal ventilationoperation which is performed during a heating operation. In the priorventilation operation, the heating operation continues to be performed.

(Air-conditioning Control Operation During Heating in Refrigerating andAir-conditioning Apparatus)

Hereinafter, specific operation examples of an air-conditioning controloperation during heating in a refrigerating and air-conditioningapparatus will be explained by way of multiple examples. As a heatingoperation performed by each refrigeration cycle, a ventilation operationis performed while performing a heating operation or only a heatingoperation is performed without performing a ventilation operation. Inthe explanation given below and FIGS. 4 to 7, a distinction is madebetween the former as heating (execution of ventilation) and the latteras heating (non-execution of ventilation).

Operation Example 1

FIG. 4 is a timing chart for explaining an operation example 1 of anair-conditioning control operation during heating in the refrigeratingand air-conditioning apparatus. The operation example 1 is an example ofthe case in which both the refrigeration cycles are performing a heatingoperation.

When both the refrigeration cycles are performing a heating operation,in the case where the defrosting start determination unit 13 ddetermines that defrosting of the outdoor heat exchanger of onerefrigeration cycle needs to start, the refrigeration cycle for which itis determined that defrosting needs to start performs theabove-described prior ventilation operation before starting thedefrosting operation. That is, by controlling the ventilation damper ofthe one refrigeration cycle side to increase the amount of ventilation,the time-averaged required amount of ventilation including the periodduring which the defrosting operation is being performed is secured.After the prior ventilation operation is terminated, the defrostingoperation is started. During the defrosting operation, the ventilationdampers 10 a and 10 b are closed so that ventilation is not performed,as described above. Then, after terminating the defrosting operation,the one refrigeration cycle returns to heating (execution ofventilation).

Furthermore, when the one refrigeration cycle starts the defrostingoperation, the other refrigeration cycle closes the ventilation damper10 b and performs heating (non-execution of ventilation). After thedefrosting operation by the one refrigeration cycle is terminated, theother refrigeration cycle returns to heating (execution of ventilation).

With the operations described above, comfort is maintained without ashortage of ventilation during the defrosting operation. Although theexample in which two refrigeration cycles are provided is illustrated asthe operation example 1, the number of refrigeration cycles is three ormore, as described above. In this case, when two or more of all therefrigeration cycles are performing a heating operation, if it isdetermined that any of the refrigeration cycles needs to startdefrosting, the refrigeration cycle that has been determined to need tostart defrosting may perform the operation of the one refrigerationcycle in FIG. 4, and the other refrigeration cycle that is performing aheating operation may perform the other refrigeration cycle in FIG. 4.

Operation Example 2

FIG. 5 is a timing chart for explaining an operation example 2 of theair-conditioning control operation during heating in theair-conditioning apparatus. The operation example 2 is an exampleapplied to the case in which when heating load is large and onerefrigeration cycle enters a defrosting operation, the heating capacityof only a heating operation of the other refrigeration cycle is notsufficient and the time-averaged required heating capacity cannot besecured.

In the operation example 2 illustrated in FIG. 5, during the period inwhich prior ventilation is performed in the operation example 1illustrated in FIG. 4, prior heating is performed at the same time asthe prior ventilation. The prior heating is an operation for securingthe time-averaged required heating capacity including the period duringwhich the defrosting operation is being performed. With the operationsdescribed above, even in the case where a defrosting operation isperformed when the heating load is large, a defrosting operation can beachieved while securing the heating capacity. Therefore, a drop in theroom temperature and a shortage of ventilation can be suppressed, thusenabling a high degree of comfort to be maintained.

Although the example in which two refrigeration cycles are provided hasbeen explained as the operation example 2, the number of refrigerationcycles may be three or more, as described above. The operation of theoperation example 2 in this case corresponds to an operation in the casewhere during the period while two or more of all the refrigerationcycles are performing a heating operation, when it is determined thatany one of the refrigeration cycles needs to start defrosting, if therefrigeration cycle that has been determined to need to start defrostingenters a defrosting operation, the heating capacity of only therefrigeration cycle that is currently performing a heating operation isnot sufficient. Therefore, the refrigeration cycle that has beendetermined to need to start defrosting may be caused to perform onerefrigeration cycle in FIG. 5, and the other refrigeration cycle that isperforming a heating operation may be caused to perform the otherrefrigeration cycle in FIG. 5.

Operation Example 3

FIG. 6 is a timing chart for explaining an operation example 3 of theair-conditioning control operation during heating in the refrigeratingand air-conditioning apparatus. The operation example 3 is an example ofthe case in which heating load is small, only one of the refrigerationcycles is performing a heating operation, and the other refrigerationcycle is stopped.

In the case where it is determined by the defrosting start determinationunit 13 d that defrosting of the outdoor heat exchanger of the onerefrigeration cycle that is performing a heating operation needs tostart, the one refrigeration cycle that has been determined to need tostart defrosting performs a prior ventilation operation, and then closesthe ventilation dampers 10 a and 10 b to start the defrosting operation,as described above.

Here, since the other refrigeration cycle is stopped, if the otherrefrigeration cycle is stopped during the period in which the onerefrigeration cycle is performing the prior ventilation operation andthe defrosting operation, heating operations in both the refrigerationcycles are stopped, and indoor heating is thus not performed. Therefore,when it is determined that the one refrigeration cycle that isperforming a heating operation needs to start defrosting, the stoppedother refrigeration cycle is driven to perform a heating operation.Then, after the one refrigeration cycle terminates the defrostingoperation, the other refrigeration cycle continues the heatingoperation. After terminating the defrosting operation, the onerefrigeration cycle stops.

With the operations described above, a defrosting operation can beachieved without a drop in the indoor temperature during the defrostingoperation, thus enabling comfort to be maintained. Furthermore, sincethe one refrigeration cycle for which defrosting needs to be performedperforms a defrosting operation and then stops and the otherrefrigeration cycle that has been stopped is caused to perform a heatingoperation instead of the one refrigeration cycle for which defrostingneeds to be performed, the operation times of the refrigeration cyclescan be equalized, thus achieving an effect of improving the reliabilityof the compressors.

Although the example in which two refrigeration cycles are provided hasbeen illustrated here, the number of refrigeration cycles may be threeor more, as described above. In this case, when only one refrigerationcycle is performing a heating operation and all the other refrigerationcycles are stopped, if it is determined that the refrigeration cyclethat is performing the heating operation needs to start defrosting, therefrigeration cycle that has been determined to start defrosting mayperform the operation of the one refrigeration cycle in FIG. 6 and anyone of the stopped refrigeration cycles may perform the operation of theother refrigeration cycle in FIG. 6. Also at this time, the stoppedrefrigeration cycle is operated so that the operation times of thecompressors can be equalized.

In the operation example 3, when the refrigeration cycle that isperforming a heating operation starts a defrosting operation, in orderto avoid an operation state in which indoor heating is not performed,the stopped refrigeration cycle is activated to perform a heatingoperation. However, the operation example 3 is not limited to this. Forexample, in an operation state in which there are five refrigerationcycles in total, three of the refrigeration cycles are performing aheating operation, and the remaining two refrigeration cycles arestopped (in other words, there are refrigeration cycles that areperforming a heating operation and refrigeration cycles that arestopped), in the case where it is determined that any one of the threerefrigeration cycles that are performing a heating operation needs tostart defrosting, either one of the two stopped refrigeration cycles maybe activated to perform a heating operation.

Operation Example 4

FIG. 7 is a timing chart for explaining an operation example 4 of theair-conditioning control operation during heating in the refrigeratingand air-conditioning apparatus. The operation example 4 is an example ofthe case in which both the refrigeration cycles are performing a heatingoperation and a decrease in the heating load is detected by anair-conditioning load detection unit.

In the case where the heating load decreases and the heating capacity ofone refrigeration cycle is sufficient, one refrigeration cycle isstopped. At this time, after causing the refrigeration cycle that is tobe stopped to perform a defrosting operation, the refrigeration cycle isstopped. Accordingly, for the next operation of the stoppedrefrigeration cycle, a heating operation can be started in the state inwhich no frost is formed on the outdoor heat exchanger of therefrigeration cycle. Therefore, the heating operation time can beextended, and thus enabling comfort to be maintained for a long time.Also in this time, the refrigeration cycle that is to perform adefrosting operation first performs a prior ventilation operation andthen performs the defrosting operation, as described in FIG. 7. Afterthe defrosting operation, the refrigeration cycle stops.

Furthermore, the function in which during the period in which onerefrigeration cycle performs a defrosting operation, the otherrefrigeration cycle performs a heating (non-execution of ventilation)operation and then returns to a heating (execution of ventilation)operation after the one refrigeration cycle terminates the defrostingoperation, is as described above. The refrigeration cycle whoseintegrated operation time of the compressor is longer of the tworefrigeration cycles may be selected as a refrigeration cycle to bestopped. Accordingly, the compressor operation times are equalized, andthe reliability of the compressors can be improved. Although the examplein which two refrigeration cycles are provided has been illustrated inthe operation example 4, the number of refrigeration cycles may be threeor more, as described above. In this case, when two or morerefrigeration cycles are performing a heating operation, if it isdetermined that any one of the refrigeration cycles needs to startdefrosting, the refrigeration cycle that has been determined to need tostart defrosting may perform the operation of one refrigeration cycle inFIG. 7, and the other refrigeration cycle that is performing a heatingoperation may perform the operation of the other refrigeration cycle inFIG. 7.

Next, control for causing a defrosting operation to be alternatelyperformed between two refrigeration cycles in the refrigerating andair-conditioning apparatus of this example will be explained.

In order to cause defrosting to be alternately performed between tworefrigeration cycles, a condition for starting a heating operation andstarting the first defrosting operation may be set different between therefrigeration cycles. More specifically, a predetermined temperaturedifference between the outside air temperature and the evaporatingtemperature, which is used for a start determination in the defrostingstart determination unit 13 d, may be set different between therefrigeration cycles. In the above description, as the startdetermination condition for a defrosting operation, the temperaturedifference between the outside air temperature and the evaporatingtemperature is set at or above 15 degrees Celsius. This value is usedfor one refrigeration cycle, and for the other refrigeration cycle, forexample, the temperature difference between the outside air temperatureand the evaporating temperature is set to at or above 13 degreesCelsius. With this setting, the timing at which defrosting startsdiffers between the refrigeration cycles. Subsequently, defrostingoperations will be started alternately.

In the refrigerating and air-conditioning apparatus, when defrostingoperations by the refrigeration cycles are alternately started at equalintervals, a variation in the room temperature is reduced to minimum,thus improving comfort. However, since the interval between starts ofdefrosting operations varies according to the state of the outside airor the operation ratio of each refrigeration cycle, it may be difficultto cause defrosting operations to be performed alternately between therefrigeration cycles at equal intervals. In this case, during a periodin which one refrigeration cycle is performing a defrosting operation orduring a predetermined time T1 after returning from the defrostingoperation to a heating operation, the other refrigeration cycle does notperform a defrosting operation even if it is determined by thedefrosting start determination unit 13 d that defrosting needs start.

Namely, after the predetermined time T1 after one refrigeration cycleterminates defrosting and returns to a heating operation, the otherrefrigeration cycle performs a defrosting operation. Therefore, thedefrosting operations of the refrigeration cycles are not simultaneouslyperformed but are alternately performed, and a heating operation cancontinue to be performed. Also in this case, a function in which a priorventilation operation is performed before a defrosting operation inorder to secure the amount of ventilation, is as described above.

Therefore, on the control, the longer one of the predetermined time T1from returning to a heating operation after one refrigeration cycleterminates a defrosting operation and the execution time of a priorventilation operation (defrosting start delay time) T2 may be selected.That is, in the case where the predetermined time T1 is shorter than thedefrosting start delay time T2, by performing a prior ventilationoperation, the function in that a defrosting operation is not performedduring the predetermined time T1 can be attained at the same time, andalternate defrosting operations between the refrigeration cycles can beachieved. In contrast, in the case where the predetermined time T1 islonger than the defrosting start delay time T2, after a priorventilation operation is performed and start of a defrosting operationis further delayed by a difference time between the predetermined timeT1 and the defrosting start delay time T2, the defrosting operation maybe started.

Although the example in which two refrigeration cycles are provided hasbeen described here, the number of refrigeration cycles may be three ormore, as described above. In this case, during the time in which atleast one of a plurality of refrigeration cycles is performing adefrosting operation or during the predetermined time T1 after returningfrom the defrosting operation to a heating operation, all the otherrefrigeration cycles may not perform a defrosting operation,

As described above, according to Embodiment 1, by providing a pluralityof refrigeration cycles that are independent from each other, adefrosting operation can be achieved while simultaneously continuing aheating operation. Furthermore, in a defrosting operation, since all theventilation ports 9 a and 9 b are closed so that the outside air is notintroduced, a drop in the room temperature during the defrostingoperation can be suppressed. Furthermore, a heating operation can beachieved while reducing the heating load during a defrosting operation.Moreover, before starting the defrosting operation, a prior ventilationoperation is performed in advance, in order to secure the time-averagedrequired amount of ventilation including the period in which thedefrosting operation is being performed, so that shortage of ventilationdoes not occur during a defrosting operation. Accordingly, even in aheating operation under air conditions leading to formation of frost, anappropriate amount of ventilation can be secured, and the comfortthrough heating can be improved.

Furthermore, since the indoor heat exchangers 7 a and 7 b and the indoorfans 8 a and 8 b of the plurality of refrigeration cycles are separatelyarranged in the indoor units 2 a and 2 b and the indoor fan of theindoor unit that is performing a defrosting operation is stopped,conventional discomfort caused by a drop in the air outlet temperaturein the case where air passing through the indoor heat exchanger of adefrosting operation side and air passing through the indoor heatexchanger of a heating operation side are mixed together in indoor unitsand the air is blown into the room, can be prevented.

In a defrosting operation, in terms of preventing a drop in the roomtemperature caused by the introduction of the outside air, it ispreferable that all the ventilation ports 9 a and 9 b are closed.However, the present invention is not necessarily limited to that inwhich all the ventilation ports are dosed. A ventilation port may beopened as long as the opening of the ventilation port does not affect adrop in the room temperature.

Furthermore, in the case where a prior heating operation for securingthe time-averaged required heating capacity including the period inwhich a defrosting operation is being performed is performed along witha prior ventilation operation before performing the defrosting operationand the defrosting operation is performed after termination of the priorheating operation and the ventilation operation, the defrostingoperation can be achieved while securing the heating capacity.Therefore, a drop in the room temperature and a shortage of ventilationcan be suppressed, thus enabling a high degree of comfort to bemaintained.

Furthermore, in the case where there is a stopped refrigeration cycleamong a plurality of refrigeration cycles, if it is determined that anyone of the refrigeration cycles that is performing a heating operationneeds to perform a defrosting operation, during the period in which therefrigeration cycle that is to perform a defrosting operation performs aprior ventilation operation and a defrosting operation, the stoppedrefrigeration cycle is activated to perform a heating operation.Accordingly, heating can be achieved even during the defrostingoperation, and the room temperature can be maintained. Furthermore, therequired amount of ventilation can be maintained, thus enabling a highdegree of comfort to be maintained,

Furthermore, when two or more refrigeration cycles of a plurality ofrefrigeration cycles are performing a heating operation and the heatingoperation of one refrigeration cycle to stop for a certain reason, forexample, a decrease in the heating load, the refrigeration cycle that isto be stopped performs a defrosting operation and is then stopped.Accordingly, for the next operation of the stopped refrigeration cycle,a heating operation can be started in the state in which no frost isformed on the outdoor heat exchanger. Therefore, the heating operationtime can be extended, thus enabling comfort to be maintained for a longtime.

Embodiment 2

(Injection Circuit)

A refrigerating and air-conditioning apparatus according to Embodiment 2is different from Embodiment 1 in the configuration of a refrigerantcircuit.

FIG. 8 is a diagram illustrating a refrigerant circuit of therefrigerating and air-conditioning apparatus according to Embodiment 2of the present invention. The configuration and control of portionsother than the refrigerant circuit are basically similar to those of therefrigerating and air-conditioning apparatus of Embodiment 1.Hereinafter, functions of Embodiment 2 that are different fromEmbodiment 1 will be mainly explained. A modification applied withrespect to the configuration and control similar to those in Embodiment1 is also applied to Embodiment 2 in a similar manner.

The refrigerant circuit of the refrigerating and air-conditioningapparatus of Embodiment 2 includes a bypass pipe 19 a that branches offbetween the indoor heat exchanger 7 a and the pressure reducing device 6a and that reaches a compression chamber of the compressor 3 a through aflow control unit 20 a, an internal heat exchanger 21 a, and a solenoidvalve 22 a, as well as the refrigerant circuit of the firstrefrigeration cycle of Embodiment 1. The internal heat exchanger 21 aperforms heat exchange between a pipe positioned between the flowcontrol unit 20 a and the solenoid valve 22 a in the bypass pipe 19 aand a pipe positioned between the indoor heat exchanger 7 a and thepressure reducing device 6 a.

Similar to the refrigerant circuit of the first refrigeration cycle, therefrigerant circuit of the second refrigeration cycle includes a bypasspipe 19 b that branches off between the indoor heat exchanger 7 b andthe pressure reducing device 6 b and that reaches a compression chamberof the compressor 3 b through the flow control unit 20 b, the internalheat exchanger 21 b, and the solenoid valve 22 b, as well as therefrigerant circuit of the second refrigeration cycle of Embodiment 1.The internal heat exchanger 21 b performs heat exchange between a pipepositioned between the flow control unit 20 b and the solenoid valve 22b in the bypass pipe 19 b and a pipe between the indoor heat exchanger 7b and the pressure reducing device 6 b.

(Cooling Operation)

Next, the operation of a cooling operation in the refrigerating andair-conditioning apparatus of Embodiment 2 will be explained. A coolingoperation is performed when the solenoid valves 22 a and 22 b areclosed. Accordingly, an operation as in Embodiment 1 is performed. Theother operations are similar to those in Embodiment 1.

(Heating Operation)

Next, the operation of a heating operation in the refrigerating andair-conditioning apparatus of Embodiment 2 will be explained. In aheating operation, the solenoid valves 22 a and 22 b are opened toperform an injection operation. The injection operation allows therefrigerant flow rate of the compressors 3 a and 3 b to increase, andallows the compressor input, that is, the heating capacity, to increase.Furthermore, in the case where the outside air temperature is low, sincethe evaporating temperature drops and the compression ratio increases,the discharge temperature rises. However, an injection operationsuppresses the discharge temperature, thus increasing the reliability ofthe compressors. Moreover, if the capacity of a compressor is variable,the capacity can be increased while suppressing the dischargetemperature, thus significantly increasing the heating capacity.

As described above, in the refrigerating and air-conditioning apparatusof Embodiment 2, by performing an injection operation during a heatingoperation, the heating capacity can be increased. Therefore, forexample, in the case where the first refrigeration cycle performs adefrosting operation and the second refrigeration cycle performs aheating operation, the advantages described below can be achieved. Thatis, by performing an injection operation in the second refrigerationcycle, the heating capacity during a defrosting operation can be securedwithout the prior heating explained in Embodiment 1 being performed inthe first refrigeration cycle.

(Defrosting Operation)

The operation of a defrosting operation in the refrigerating andair-conditioning apparatus of Embodiment 2 will now be explained. Adefrosting operation is performed when the solenoid valves 22 a and 22 bare closed. Accordingly, an operation as in Embodiment 1 is performed.The other operations are similar to those in Embodiment 1.

According to Embodiment 2, advantages similar to those in Embodiment 1are attained. In addition, in starting a defrosting operation in any oneof refrigeration cycles in the refrigerating and air-conditioningapparatus, by performing an injection operation on a heating operationside, the required heating capacity can be secured without performing aprior heating operation to secure the time-averaged required heatingcapacity on the defrosting operation side.

Furthermore, in a situation in which one refrigeration cycle performs aheating operation while the other refrigeration cycle is performing adefrosting operation, for example, the outdoor fan 12 may be caused tobe stopped, for example, when the outside air temperature is low. Atthis time, by performing an injection operation in the refrigerationcycle on the heating operation side, as described above, even if theevaporating temperature drops due to the stoppage of the outdoor fan 12,the heating capacity can be increased. Even in this case, the requiredheating capacity can be secured without performing prior heating on thedefrosting operation side. Therefore, when the outside air temperatureis low, a defrosting operation which secures the heating capacity can beachieved while suppressing a rise in the discharge temperature byinjection, thus securing a high reliability.

Although the example in which two refrigeration cycles are provided isillustrated in FIG. 8, the number of refrigeration cycles may be threeor more. Also in this case, similar operation effects can be achieved.

REFERENCE SIGNS LIST

1: outdoor unit, 2 a: indoor unit, 2 b: indoor unit, 3 a: compressor, 3b: compressor, 4 a: four-way valve, 4 b: four-way valve, 5 a: outdoorheat exchanger, 5 b: outdoor heat exchanger, 6 a: pressure reducingdevice, 6 b: pressure reducing device, 7 a: indoor heat exchanger, 7 b:indoor heat exchanger, 8 a: indoor fan, 8 b: indoor fan, 9 a:ventilation port, 9 b: ventilation port, 10 a: ventilation damper, 10 b:ventilation damper, 11 a: air inlet, 11 b: air inlet, 12: outdoor fan,13: controller, 14 a: indoor temperature sensor, 14 b: indoortemperature sensor, 15 a: indoor humidity sensor, 15 b: indoor humiditysensor, 16 a: outside air temperature sensor, 16 b: outside airtemperature sensor, 17 a: temperature sensor, 17 b: temperature sensor,18: input unit, 19 a: bypass pipe, 19 b: bypass pipe, 20 a: flow controlunit, 20 b: flow control unit, 21 a: internal heat exchanger, 21 b:internal heat exchanger, 22 a: solenoid valve, 22 b: solenoid valve

1. A refrigerating and air-conditioning apparatus comprising: aplurality of refrigeration cycles that each include a compressor, afour-way valve, an outdoor heat exchanger, a pressure reducing device,and an indoor heat exchanger that are connected to one another, theplurality of refrigeration cycles being capable of independentlyperforming a heating operation and a defrosting operation; a pluralityof indoor units each provided with the indoor heat exchanger that isincluded in each of the plurality of refrigeration cycles, the pluralityof indoor units that each include an indoor fan for taking in outsideair through the ventilation port and sending the air into a room, and aventilation damper for opening and closing the ventilation port; and acontroller that controls the ventilation damper to perform indoorventilation during the heating operation, and that controls theventilation damper of each of the plurality of indoor units to close thecorresponding ventilation port and stop indoor ventilation during adefrosting operation, wherein the plurality of indoor units areinstalled in the same room, and wherein prior to a defrosting operation,the controller performs a prior ventilation operation to increase theamount of ventilation by controlling the ventilation damper of theindoor unit of a refrigeration cycle that is to perform the defrostingoperation, and after termination of the prior ventilation operation, thecontroller starts the defrosting operation.
 2. The refrigerating andair-conditioning apparatus of claim 1, wherein, in a case where there isa stopped refrigeration cycle of the plurality of refrigeration cyclesand a refrigeration cycle that is performing the heating operation toperform a defrosting operation, the controller activates the stoppedrefrigeration cycle and causes the stopped refrigeration cycle toperform the heating operation during a period in which the refrigerationcycle that performs the defrosting operation is performing the priorventilation operation and the defrosting operation.
 3. The refrigeratingand air-conditioning apparatus of claim 2, wherein after activating thestopped refrigeration cycle to start the heating operation, thecontroller causes the heating operation to continue to be performed evenafter the refrigeration cycle that performs the defrosting operationterminates the defrosting operation, and causes the refrigeration cyclethat performs the defrosting operation to stop operating aftertermination of the defrosting operation.
 4. The refrigerating andair-conditioning apparatus of claim 1, wherein the controller, in orderto stop the heating operation of any one of at least two or morerefrigeration cycles that are performing the heating operation among theplurality of refrigeration cycles, before stopping the heatingoperation, performs the prior ventilation operation and the defrostingoperation and then stops the heating operation.
 5. The refrigerating andair-conditioning apparatus of claim
 1. wherein by controlling therefrigeration cycle that is to perform a defrosting operation to controla heating capacity before performing the defrosting operation, thecontroller performs, along with the prior ventilation operation, a priorheating operation for securing a time-averaged required heating capacityincluding a period during which the defrosting operation is beingperformed, and starts the defrosting operation after termination of theprior heating operation and the ventilation operation.
 6. Therefrigerating and air-conditioning apparatus of claim 1, wherein as thedefrosting operation, the controller controls the four-way valve toallow a refrigerant to flow in a direction opposite a direction in whicha refrigerant flows during the heating operation.
 7. The refrigeratingand air-conditioning apparatus of claim 6, wherein the controller, in adefrosting operation, stops the indoor fan of the indoor unit of arefrigeration cycle that is to perform the defrosting operation, andstops an outdoor fan for sending air to the outdoor heat exchanger to besubjected to defrosting.
 8. The refrigerating and air-conditioningapparatus of claim 6, wherein the controller, in a defrosting operation,operates the indoor fan of the indoor unit of a refrigeration cycle thatis to perform the defrosting operation, when heating load is smallerthan or equal to a predetermined value, and stops the indoor fan of theindoor unit when the heating load is greater than the predeterminedvalue.
 9. The refrigerating and air-conditioning apparatus of claim 6,further comprising: an outside air temperature detecting sensor, whereinthe controller, in a defrosting operation, operates an outdoor fan forsending air to the outdoor heat exchanger to be subjected to defrostingwhen an outside air temperature detected by the outside air temperaturedetecting sensor is at or above a predetermined value, and stops theoutdoor fan for sending air to the outdoor heat exchanger to besubjected to defrosting when the outside air temperature detected by theoutside air temperature detecting sensor is below the predeterminedvalue.
 10. The refrigerating and air-conditioning apparatus of claim 1,further comprising an outside air temperature detecting sensor, whereinin a case where an outside air temperature detected by the outside airtemperature detecting sensor is at or above a predetermined value, asthe defrosting operation, the controller stops the compressor andoperates an outdoor fan for sending air to the outdoor heat exchanger tobe subjected to defrosting.
 11. The refrigerating and air-conditioningapparatus of claim 1, further comprising: a bypass pipe that branchesoff between the indoor heat exchanger and the pressure reducing deviceand that reaches a suction side of the compressor via a flow controlunit; and an internal heat exchanger that exchanges heat between arefrigerant between the indoor heat exchanger and the pressure reducingdevice and a refrigerant that has passed through the flow control unitin the bypass pipe, wherein in the heating operation, part of therefrigerant between the indoor heat exchanger and the pressure reducingdevice is allowed to flow into the bypass pipe and to be compressed bythe flow control unit, and after the compressed refrigerant is subjectedto heat exchange with the refrigerant between the indoor heat exchangerand the pressure reducing device in the internal heat exchanger, thecompressed refrigerant that has been subjected to heat exchange isinjected to a compression chamber of the compressor.
 12. Therefrigerating and air-conditioning apparatus of claim 1, wherein duringa period in which at least one of the plurality of refrigeration cyclesis performing a defrosting operation or a predetermined period of timeafter returning from the defrosting operation to the heating operation,none of the plurality of refrigeration cycles performs a defrostingoperation.
 13. The refrigerating and air-conditioning apparatus of claim1, wherein in the prior ventilation operation, the controller secures atime-averaged required amount of ventilation including a period in whichthe defrosting operation is being performed by controlling theventilation damper of the indoor unit of a refrigeration cycle that isto perform the defrosting operation to increase the amount ofventilation.